I have a 1974 360 I'm having rebuilt. I heard the 360 is externally balanced by the torque converter. If this is true, will balancing the crankshaft affect the way the engine runs (cause vibration). Do I have my facts right? Thanks
Thank you for the thorough response.The 360 takes a special balancer and usually a torque converter with a weight welded on to it. Alternately you can use a flex plate with a section removed...
In either case your engine balancer (machinist) should have, and use, all the components of the rotating assembly to balance the crank. This includes the pistons, rods, balancer, and t-converter, or flex plate. He may not mount these items, but does need their weight.
I had the machine shop balance the crank. One of the older machinist informed the younger machinist that you need a weighted flex plate when you balance the 360 crank. Luckily the old timer intervened or my crank would be out of balance.Interestingly, we just went a few rounds with this issue with Eagle Specialty Products as ordered from Summit Racing.
We ordered what is advertised (at least as far back as 2012 and currently) as an "externally balanced" ESP crankshaft from Summit for a 1972 360. Machinist got it ready to go on the balancing machine and called to say "you got an internally balanced shaft."
Numerous Customer Service communications with both Summit and Eagle taught us that Eagle claims "externally balanced" was a misprint and that they have NEVER sold an externally balanced crank for the 360.
I personally found that hard to believe, but had no choice but to take them at their word. Thus we started moving toward converting this engine to internally balanced rotating assembly.
As I am now having another, separate crankshaft issue with the Eagle/Summit pairing, I may have to source the crank for this engine elsewhere. If there is as source of a cast, externally balanced crank, I'm open to suggestions.
My point is watch what you are getting when ordering parts.
I believe Mopar sells the 360 cranks, 3.58 and stroker too.Interestingly, we just went a few rounds with this issue with Eagle Specialty Products as ordered from Summit Racing.
We ordered what is advertised (at least as far back as 2012 and currently) as an "externally balanced" ESP crankshaft from Summit for a 1972 360. Machinist got it ready to go on the balancing machine and called to say "you got an internally balanced shaft."
Numerous Customer Service communications with both Summit and Eagle taught us that Eagle claims "externally balanced" was a misprint and that they have NEVER sold an externally balanced crank for the 360.
I personally found that hard to believe, but had no choice but to take them at their word. Thus we started moving toward converting this engine to internally balanced rotating assembly.
As I am now having another, separate crankshaft issue with the Eagle/Summit pairing, I may have to source the crank for this engine elsewhere. If there is as source of a cast, externally balanced crank, I'm open to suggestions.
My point is watch what you are getting when ordering parts.
I ended up having to buy a new crank for my 340. The previous rebuild, prior to my ownership, tried to convert to internal balance and forever screwed up the crank. I found similar issues as all aftermarket cranks I found, that didn't cost 800 bucks or more, were internal balanced. I got into discussion with machinist and his balancing specialist and determined we could get everything to work the internal balance crank and other external balance components I had purchased. End result, crank is balanced to within .04 oz-inch. Damn nearly good enough for pro stock racing.Interestingly, we just went a few rounds with this issue with Eagle Specialty Products as ordered from Summit Racing.
We ordered what is advertised (at least as far back as 2012 and currently) as an "externally balanced" ESP crankshaft from Summit for a 1972 360. Machinist got it ready to go on the balancing machine and called to say "you got an internally balanced shaft."
Numerous Customer Service communications with both Summit and Eagle taught us that Eagle claims "externally balanced" was a misprint and that they have NEVER sold an externally balanced crank for the 360.
I personally found that hard to believe, but had no choice but to take them at their word. Thus we started moving toward converting this engine to internally balanced rotating assembly.
As I am now having another, separate crankshaft issue with the Eagle/Summit pairing, I may have to source the crank for this engine elsewhere. If there is as source of a cast, externally balanced crank, I'm open to suggestions.
My point is watch what you are getting when ordering parts.
I believe the 360 is the only engine that is externally balanced. Why? I don't know.IAnd of big blocks? I have a B-block 400 with a 440 crank. I know it was balanced and had to cut the counter weights down to balance for short deck motor use. (Poor man's stroker.) But I don't believe the flex plate has any weight added? Or consideration to the crank balance?
Interesting. I'm willing to bet its a factory money thing?I believe the 360 is the only engine that is externally balanced. Why? I don't know.I
You're right. I looked it up online. The last year of the 340 cast cranks were externally balanced. Not sure about the 400 big block.I don’t think that is correct. Weren’t late 340s, and 400 big blocks, externally balanced?
That option only makes sence. If there wasn't a factory option? Aftermarket would have jumped all over that.If you are building a late 340 you can upgrade the crank with the factory forged one and add an internally balanced harmonic balancer and flywheel quite easily like these guys did.
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